1. Field of the Invention
The present invention generally relates to laser interrogator systems and techniques for identification friend or foe (IFF) and more specifically, to a laser retroreflector pulse delay line system and technique for IFF.
2. Description of Prior Art
It is essential to positively identify friendly forces quickly, accurately and in a low observable manner with absolute assurance in order to effectively engage those unfriendly forces. The uncertainly in the identification of forces on the battlefield and subsequent hesitation in engagements can lead to an ineffective encounter, fratricide in the worst case. With the advent of increased availability of sophisticated electronics to unfriendly forces, the low observable requirement for such IFF systems and techniques to unfriendly forces become more difficult to achieve without the use of more sophisticated electronics and mechanical devices.
Currently, there is no known fielded low observable IFF system that is simple, rugged and very low cost. Several high-observable alternatives exist, such as thermal tape, near-infrared lights (NIR) lights, thermal beacons, etc. which can be viewed by all parties on the battlefield, both friendly and unfriendly. Prior art laser interrogator schemes utilize active systems which include sophisticated electronics and mechanical devices such as complex arrays of retroreflectors, mechanical or electrical driven shutter devices. Some systems depend on signal returns at some other wavelength (such as millimeter or microwave), and rely on complicated electronic processing. These systems are complicated, fragile, and very costly. Since a typical system would have to withstand tremendous impact forces during battlefield conditions, there is yet devised a practical IFF system.
While the prior art has reported using laser interrogator systems and techniques for IFF, none have established a basis for a specific technique and apparatus that is dedicated to the task of resolving the particular problem at hand. What is needed in this instance is a low observable laser interrogator system and technique that requires no mechanical moving parts or electrically powered components for the targeted platform.